Due to the hectic lifestyles and changing practices many new mothers have, a great number of women in the US are not successful with their breastfeeding journeys. Understanding the anatomy and physiology of breastfeeding is essential to all mothers for them to know how to solve their nursing issues accordingly. This nifty guide will explain to you succinctly everything you need to know about the anatomy and physiology of breastfeeding!

Breast milk is the best and most natural way of nourishing your baby. Since it’s the optimum form of infant nutrition, many major health organizations including the American Academy of Pediatrics (AAP) and the World Health Organization (WHO) recommend breastfeeding exclusively for the first 6 months of life, and complementary feeding along with breast milk for at least one year.

How Breastfeeding Works In A Nutshell…

Your breasts begin to develop during puberty and change drastically when you become pregnant. The changes are driven by certain hormones in preparation for breastfeeding.
Estrogen, progesterone, prolactin, oxytocin are the four essential hormones needed in producing breast milk. They act on varying stages of your breastfeeding so that you can synthesize, store, and express your breast milk.
Lactation is primarily driven by hormones in the beginning, but after delivering the baby, it will be the mother’s responsibility to maintain milk supply. Breastfeeding and pumping out breast milk is important to maintain adequate breast milk for your baby.
Breast milk changes through time to respond to your baby’s nutrient needs. It consists of a powerful combination of nutrients and antibodies for your child’s growth and development as well as protection against diseases.

Story Time

Before I was a mom I just thought that once you had a baby your boobs would just automatically be filled with milk and that was that. To me, it was just a natural process.

In theory, it may seem simple but it takes a lot of things to happen in your body in order for you to make breast milk. It’s only then that you realize how amazing and incredible it is that every breast milk is tailor-made for each baby. In fact, even the color and texture changes from baby to baby. With Samuel, my milk always had a much more yellow color than with Isaac. Yet, I was the same person making it! That was always so cool for me to see.

Anatomy and Physiology of Breastfeeding: Changes During Pregnancy and Lactation

Your breasts undergo extensive changes throughout your lifetime. Even while you were in the womb of your mother, your milk ducts, which consist of a network of canals acting as a milk transporter, have already started to develop. However, its functions only begin by puberty. During your teens, hormonal changes cause your breasts to develop in size.

Every set of breasts grows differently in size and shape. It is made up of supportive tissues, milk glands, and protective fat layers. Under all the fat cells and glandular tissues are milk ducts composed of a complex network of channels. The ducts then branch off into ductules, which are smaller channels near the chest wall. At the end of each ductule are clusters of small sacs called alveoli.

The first major change in your breasts happens during pregnancy. In the first trimester, there will be a rapid growth of the ductal-lobular-alveolar system in the breasts. Every woman and each pregnancy will vary in the timing and degree of glandular growth. Although the most extensive breast growth happens in the first three months, you will still notice a gradual development in the succeeding trimesters. By the time you near your due date, glandular luminal cells begin to actively synthesize breast milk.

Does Breast Size Matter?

It might be worrying for flat-chested or busty girls to breastfeed as they may think their breast size has an effect on the amount of breast milk they can produce. But the truth is, the size of your breasts does not determine the quantity of breast milk you can make. Studies have found that there is no relation between the growth of your breast during pregnancy and the amount of milk the breast can produce during the 1st month of lactation.

Moreover, the size of your boobs does not also correspond to your milk storage capacity. The alveolar cells, which stores breast milk, can cover a wide range of milk volume from 80 up to 600 millimeters.

How Does Breastfeeding Work?

Your breast will kick start milk production the moment you become pregnant. The whole breastfeeding process is driven by four main hormones working together to produce and eject the breast milk for your baby. In addition, the breast milk undergoes different changes in terms of its composition to adjust to your baby’s nutrient needs.

Hormones Involved With Lactation

Breastfeeding is a complex biological process involving a delicate balance of four hormones namely: estrogen, progesterone, prolactin, and oxytocin. The body will be able to do the necessary adjustments in the level of these hormones in order to make, store, and eject breast milk.

Estrogen and Progesterone

Estrogen and progesterone share in the responsibility to make the breast milk. They are released by the placenta when you become pregnant. These two hormones are tasked to do two things. First, they will increase the size and number of milk ducts in the breasts. Next, they need to regulate breast milk production so you’re not oversupplying while you are pregnant. When the baby and the placenta is delivered, your estrogen and progesterone levels will eventually decrease. The drop in these hormones will signal your body to produce more milk.

Prolactin

Prolactin also works for breast milk production. After giving birth, the prolactin levels in your body will increase. High levels of prolactin will signal your breast to synthesize and store breast milk in the breast alveoli. In order to keep the prolactin levels high and keep a steady milk supply, it’s important to continue to breastfeeding and pump frequently as soon as you have delivered the baby.

Oxytocin

The hormone responsible for releasing milk from your breast is oxytocin. The baby’s latch and suction trigger oxytocin to be released. This will then signal the breast milk to be squeezed out of the alveoli, towards the ducts, ejected out of your nipple, and onto your baby’s mouth. This process is called the Milk Ejection or Let-Down Reflex.

Stages of Lactogenesis

Milk production or lactogenesis occurs in various stages. From the time you are pregnant up until the moment you give birth, your breasts work through different phases in preparation for breastfeeding. The stages are as follows:

Lactogenesis I

This phase occurs from 15 up to 20 weeks of gestation. In this stage, your hormones are in hyperdrive to get your breasts ready to produce milk. All the components of breast milk can be synthesized at this stage. The first milk (colostrum) can be produced halfway through the pregnancy. Some moms take advantage of this stage in order to collect and store breast milk through hand expressions. Expressing breast milk even while you are pregnant has been proven beneficial especially for moms who anticipate breastfeeding issues.

Lactogenesis II

A day or two after giving birth, lactogenesis II begins. It starts once the baby and the placenta are delivered. Prolactin and other hormones like insulin, cortisol, thyroxine, and oxytocin work together in preparation for the actual breastfeeding. Most moms will start to feel their breasts becoming fuller 2 to 4 days after delivery.

Lactogenesis III

While lactogenesis I and II are hormonally driven, lactogenesis III occurs and continues only when the milk is regularly removed from the breasts. This means that this phase is entirely under the control of the mother and will continue to occur as long as the mother actively breastfeeds or pumps out breast milk.

The Milk Ejection or Let-Down Reflex

As a neuroendocrine reflex, the Milk Ejection or Let-Down Reflex is important to establish and maintain an adequate supply of breast milk. This reflex happens whenever your baby starts sucking and stimulating your nipple and areola. This act triggers the release of oxytocin which then signals the muscles around the milk-making tissues to contract and push out breast milk from the milk ducts to the nipple.

The MER or let-down reflex can feel different for every mom. Some mothers only get to feel this when their baby latches and sucks on their nipples. Other signs that the MER is being activated include:

Feeling a tingling sensation in the breast
Slight prickling or pain in the breast
Having little leaks from the other breast
Feeling thirsty
Cramping and tightening in their uterus

At the beginning of a nursing session, the baby shallowly sucks the nipple but gradually develops to deep rhythmic swallows once the breast milk starts flowing. In order to stimulate the let-down reflex, breast milk has to be regularly removed. This is why it’s important to breastfeed and pump often.

Breast Milk Composition and Changes

Your breast milk consists of a very dynamic and efficient nutrient composition that responds to the growth and development of your child. Many experts believe that every breast milk can vary in composition because it is uniquely tailored by each mom to meet the specific needs of their child.

How Your Breast Milk Changes Over Time

Breast milk is basically personalized nutrition for your baby! During their first few years, they go through advanced changes and development which require adjustments in terms of their nutrient needs as well. Here’s how your breast milk changes over time:

Colostrum or The First Milk

The first milk you express is the colostrum which is a thick, yellowish, and sticky substance. You only express a small amount of this liquid, but it’s definitely packed optimally to include everything that your newborn needs.

The colostrum provides a more immunological benefit in order to protect your baby for infections that his/her body aren’t prepared for. In composition, it includes antibodies, bioactive cells, good bacteria, human oligosaccharides, and other protective cells.

Transitional Milk In The First Few Weeks

Colostrum will then transition right in the first few weeks after delivery. You will notice a drastic change in breast size because you will be expecting to produce more milk. The breast milk also becomes creamier in consistency as the fat content of the milk also increases. It will also have greater amounts of lactose and calories to meet your baby’s fast-growing demands.

Mature Milk In The First Month Onwards

By the fourth week, your milk becomes more mature and the composition will remain stable. It will be high in lactose, proteins, vitamin, and minerals. However, over your breastfeeding journey, small changes in composition can occur every feed and throughout your child’s growth.

What’s In Your Breast MIlk?

Mature breast milk is perfect in its nutrient composition. It’s composed of water, fat, carbohydrate, proteins, vitamins, minerals, and essential amino acids. It also has immunity building properties like white blood cells, antibodies, enzymes, and other substances to strengthen your baby’s immune system. What’s more amazing is that all its components can’t be manufactured in a lab! That’s why no infant formula can beat the power of breast milk.

Breast milk has over 200 known beneficial components. Studies have found that the nutrients in breast milk do not just provide nutrition to your baby, but also serve other functional benefits. For instance, the fatty acid found in breast milk helps in promoting brain development and may even enhance your baby’s cognition.

Here are some more substances that constitute breast milk:

Millions of live cells that boost immunity including white blood cells
Over a thousand types of protein to help your baby grow and develop
20 amino acids which also helps in the development of tissues and organs in the body
More than 200 complex sugars or oligosaccharides, including prebiotics that protect and strengthen the baby’s gut.
40 and more enzymes that speed up the metabolic and chemical reactions in the body
Growth factors that support healthy growth and development
Hormones that send the signals between tissues and organs to ensure they are functioning right. They also help in regulating biological processes like the baby’s appetite or sleep
Immunoglobulins or antibodies that protect your baby against sickness and infections
Long-chain fatty acids that are essential in building your baby’s nervous system
MicroRNAs which regulate the baby’s gene expression, prevent diseases and support immunity

Factors Affecting Breast Milk Composition

There are so many factors that can affect the composition of your breast milk. Depending on the stage at which you are breastfeeding, and even the time of the day, your breast milk adjusts accordingly to your baby’s need. Here are some of the factors:

Baby’s Age. As your baby grows, your breast milk changes as well. As mentioned earlier, breast milk changes from colostrum to transitional milk, which then becomes the mature milk after the first month.
Timing of feeding. There is a change in fat content in the beginning and end of every feed. The breast milk your produce at the start of the feed is called the foremilk. On the other hand, the hindmilk is the milk you lactate at the end of the feed. They technically have no drastic distinction other than the amount of fat. The hindmilk usually has a higher fat content over the foremilk. Since fat is an important nutrient for your baby, it’s essential to express and empty your breast so your child gets all the nutrients they need.
Time of the day. Some reports have shown that the fat content of breast milk is relatively higher during mid-morning and is lowest during the night.
Mother’s Nutrition. The diet of the mother highly influences breast milk composition. The breast milk fat content can even change and mimic the dietary fat the mother consumes within 2-3 days. That’s why it’s also essential for the mom to prioritize her own diet and nutrition as well.
Baby’s Weight At Birth. Fat content has been found higher in babies with low and high birth weight. However, the protein and carbohydrate content does not get affected by the baby’s birth weight.

In Conclusion…

Breastfeeding is a natural biological process, but that doesn’t mean it’s easy to do. Many mothers encounter different breastfeeding problems mostly because they did not prepare and are clueless about what to expect. Understanding the anatomy of breastfeeding and the physiology of lactation is essential so that you can achieve a successful breastfeeding journey.

At puberty, your breast starts to develop preliminary tissues and glands in preparation for when you are pregnant. During pregnancy, the release of hormones triggers your breast to change in anticipation for breastfeeding. With the help of the milk-making hormones, lactogenesis or milk production occurs even while you are pregnant and continues on during the first few hours after delivery. From then, it becomes the duty of the mother to express and empty her milk in order to achieve an adequate milk supply. The milk ejection or let-down reflex, which is stimulated by the baby’s latch, signals the milk to flow from your breast to your baby.

Your breasts aren’t the only ones changing while you breastfeed. The composition of your breast milk also adjusts according to your baby’s needs. Breast milk is truly amazing as every mom has tailor-made breast milk for their baby, consisting of a powerful combination of nutrients and immunity-boosting substances to develop and protect your baby. However, there are varying factors that may also affect the mother’s breast milk. It’s important to practice good nursing and lifestyle habits so you can breastfeed with ease.